1. Field of the Invention
The present invention relates to a foldable chair frame, more particularly to a foldable chair frame provided with a locking unit for locking the chair frame at an unfolded state so as to prevent untimely folding of the chair frame.
2. Description of the Related Art
FIG. 1 shows a conventional chair frame 1 which includes a generally horizontal seat member 11, a front leg member 13 with an upper end pivoted to a front portion of the seat member 11 by means of a front pivot axle 12, and a rear leg member 14 with an upper end pivoted to a rear portion of the seat member 11 by means of a rear pivot axle 12'. A front linking unit 15 and a rear linking unit 15' are disposed between the front and rear leg members 13, 14 for connecting foldably the front and rear leg members 13, 14 to the seat member 11 such that the front leg member 13 is foldable rearwardly toward the seat member 11 and such that the rear leg member 14 is foldable forwardly toward the seat member 11. As shown in FIG. 2, each of the front and rear linking units 15, 15' includes a first linking plate 151 having an upper end pivoted to the seat member 11 by means of a horizontal first pivot pin 154, and a second linking plate 152 having an upper end pivoted to a lower end of the first linking plate 151 by means of a horizontal second pivot pin 153 and a lower end pivoted to an intermediate section of a respective one of the front and rear leg members 13, 14 by means of a horizontal third pivot pin 154'. The lower end of the first linking plate 151 is formed with a stop projection 155 for engaging an engaging groove 156 formed in the upper end of the lower linking plate 152 so as to limit further pivoting movement between the first and second linking plates 151, 152 when the first and second linking plates 151, 152 are unfolded from each other (see FIG. 1). By unfolding the first and second linking plates 151, 152 from each other, the respective one of the front and rear leg members 13, 14 can be unfolded from the seat member 11. To fold the chair frame 1, the juncture portions of the first and second linking plates 151, 152 are pushed upwardly to disengage the stop projection 155 from the engaging groove 156 and to result inpivoting movement of the first and second linking plates 151, 152 relative to each other, thereby folding the front or rear leg member 13, 14 toward the seat member 11.
However, since the first and second linking plates 151, 152 are not locked to each other at the unfolded state, it is likely that the front and rear leg members 13, 14 might be untimely folded toward the seat member 11. This could happen when the chair frame 1 is disposed on an uneven ground surface, such as on the beach. As such, user safety cannot be ensured.